Present day manufacturers of logic circuits have to work with numbers of discrete components or complicated integration of their function to create devices suitable for selectable direct interface to either TTL or CMOS logic in operation of MOS and TTL circuit elements.
Acutally the prior art requires components external to such IC devices, i.e. resistors, transistors and in some cases diodes. Other examples of known prior art are devices which are designed so as to have transistors of variable threshold as would be required in considering TTL mode and/or CMOS mode capability. However, with such devices it is not possible to control the circuit threshold independently of signal input especially if in a system where free time for conditioning the buffer is not available.
Other known circuits show two terminal devices intended to produce negative resistance. In such the applied bias signal will be some fraction of the applied signal voltage.
Also known are circuits which operate with bipolar devices, circuits using more than one substrate region being maintained at more than one voltage, and circuits to control electrical power displays.